The aye-aye, a type of lemur with an unusually long finger, uses its elongated digit to have quite a dirty habit - picking its nose. Usually, it uses its impressive finger to hunt grubs, but Professor Anne-Claire Fabre has noticed it also inserts it into its nose - pushing it so far back it disappears. Prof. Fabre was curious about the behaviour and conducted 3D anatomical analysis of the aye-aye's head, to reconstruct the seemingly impossible habit. She found its finger was going beyond its nose and into the sinus and from the sinus into the throat and into the mouth. With her colleagues, Prof Fabre searched scientific literature for evidence of other animals that pick their noses and in a study published in the Journal of Zoology. They found 12 examples of primates caught nose-picking. Despite this, scientists remain mystified why primates, including humans, pick their nose - and the scientist is looking to find out the evolutionary benefits of doing so. One study, however, suggested it may be good for you as the ingestion of nasal mucus could play an important role in strengthening the immune system.